Catalytic Isoforms Tpk1 And Tpk2 Of Candida Albicans PKA have non redundant Roles in Stress Response And Glycogen Metabolism

ROMINA GIACOMETTI; SUSANA PASSERON

Aguas de Lindoia, Sao Paulo, Brasil

Congreso; XXXVII Annual Meeting of the Brazilian Society for Biochemistry and Molecular Biology (SBBq) a joint event with the XI Congress of the Panamerican Association for Biochemistry and Molecular Biology (PABMB); 2008

Candida albicans is a fungal organism that is found in healthy humans but can prompt severe systemic infections in immuno-compromised individuals. The cAMP dependent protein kinase (PKA) from C. albicans is coded by two catalytic subunits (TPK1 and TPK2) and one regulatory subunit (BCY1). In C. albicans, cAMP signaling mediates basic cellular processes such as the yeast to hyphae transition and cell cycle. Therefore, it is of interest to depict the molecular details of C. albicans PKA regulation and action, to better evaluate its potential as a drug target. In the present study, we investigated the role of C. albicans PKA in glycogen metabolism, as well as in response to heat or saline stress and to nutrient deprivation. In order to fine-tune the analysis, we performed the study on mutants devoid of the two gene copies of TPK1 or TPK2 and also in mutants of TPK1 and TPK2 on a different background of regulation by Bcy1p. We found that hetero and/or homozygous tpk1 strains developed a lower tolerance to saline exposure, while tpk2 mutants were resistant to this stress, indicating that both isoforms play different roles in the osmotic stress response pathway. Surprisingly, we also found that those strains devoid of one or both TPK1 alleles were defective in glycogen storage, while strains lacking Tpk2p accumulated higher levels of the polysaccharide, indicating that Tpk1p and Tpk2p have opposite roles in carbohydrate metabolism. Finally, in vitro kinase assays uncovered conditions where Tpk1p vastly increased its specific activity independently of cAMP in a defective mutant tpk2 TPK1/tpk1 BCY1/bcy1.